The field of the invention relates to fabricating integrated circuits (ICs); more particularly, the present invention relates to fabricating radio-frequency (RF) ICs.
Communication systems employ transmitters and receivers to transfer information over some media. When communications occur over atmosphere, or air waves, they are commonly referred to as xe2x80x9cwirelessxe2x80x9d communications. One type of wireless communication is radio-frequency (RF) communication. Today, the frequencies at which RF communication may be used has become quite high. It is not uncommon to see RF frequencies in the Gigahertz range.
Problems may arise on integrated circuit designs for RF devices. For example, the RF signals being received and transmitted may interfere with other signals on a chip. Parasitic capacitances can limit the frequency of the RF signal. Such interference increases as the frequency of the RF signals increases.
A radio-frequency (RF) integrated circuit is described. In one embodiment, the IC comprises multiple metal layers forming multiple transistors on a substrate. The transistors are step and mirror symmetric. Also, the RF signal lines are on a top metal layer above all other metal layers and the power and ground planes are on a bottom metal layer below all other metal layers. The top and bottom metal layers are separated by a shield that extends beyond the RF signal lines by a distance that is at least the same distance that the shield is away from the RF lines. Low frequency signals are on signal lines below the top metal layer.